Octadecyl acrylate based block and random copolymers prepared by ATRP as comb-like stabilizers for colloidal micro-particle one-step synthesis in organic solvents

Three random and three block copolymers of methyl methacrylate (MMA) and octadecyl acrylate (ODA) were synthesised by atom transfer radical polymerisation. These copolymers were assessed for their application as stabilizers in the one-step non-aqueous dispersion polymerisation of MMA in a non-polar solvent mixture of hexane and dodecane. In all cases stable spherical micro-particle colloidal dispersions were formed with particle diameters in the range of 400-2730 nm. Uniform monodisperse particles with standard deviations in size distributions of less than 5% were obtained in two cases demonstrating the utility of ODA:MMA copolymers as replacement preformed stabilizers in the one-step synthesis of MMA micro-spheres.     

Preparation of monodisperse PMMA particles by dispersion polymerization of MMA using poly(styrene-co-methacrylic acid) copolymer as a steric stabilizer

Dispersion polymerization of MMA was conducted using poly(styrene-co-methacrylic acid) copolymer as a steric stabilizer in an aqueous methanol medium. Various composition copolymers were easily prepared with a conventional radical polymerization by changing the monomer ratios of styrene to methacrylic acid, and were employed as a steric stabilizer for dispersion polymerization. The copolymers prepared with monomer ratios of 1.25–1.50 were found to be suitable steric stabilizers for dispersion polymerization. A very small amount of copolymer (0.6 wt% based on MMA) could act as a steric stabilizer effectively to obtain monodisperse PMMA particles. The particle size decreased with increasing the solvent polarity from 4 to 0.14 μm.     

Synthesis of well‐defined poly(methyl methacrylate) nanoparticles by reverse atom transfer radical polymerization in a microemulsion

Well‐defined poly(methyl methacrylate) (PMMA) with an α‐isobutyronitrile group and an ω‐bromine atom as the end groups was synthesized by the microemulsion polymerization of methyl methacrylate (MMA) at 70°C with a 2,2′‐azobisisobutyronitrile/CuBr₂/2,2′‐bipyridine system. The conversion of the polymerization reached 81.9%. The viscosity‐average molecular weight of PMMA was high (380,000), and the polydispersity index was 1.58. The polymerization of MMA exhibited some controlled radical polymerization characteristics. The mechanism of controlled polymerization was studied. The presence of hydrogen and bromine atoms as end groups of the obtained PMMA was determined by ¹H‐NMR spectroscopy. The shape and size of the final polymer particles were analyzed by scanning probe microscopy, and the diameters of the obtained particles were usually in the range of 60–100 nm. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3670–3676, 2006     

Synthesis and characterization of amphiphilic block copolymers of methyl methacrylate with poly(ethylene oxide) macroinitiators formed by atom transfer radical polymerization

Amphiphilic ABA triblock copolymers of poly(ethylene oxide) (PEO) with methyl methacrylate (MMA) were prepared by atom transfer radical polymerization in bulk and in various solvents with a difunctional PEO macroinitiator and a Cu(I)X/N,N,N′,N″,N″‐pentamethyldiethylenetriamine catalyst system at 85°C where X=Cl or Br. The polymerization proceeded via controlled/living process, and the molecular weights of the obtained block copolymers increased linearly with monomer conversion. In the process, the polydispersity decreased and finally reached a value of less than 1.3. The polymerization followed first‐order kinetics with respect to monomer concentration, and increases in the ethylene oxide repeating units or chain length in the macroinitiator decreased the rate of polymerization. The rate of polymerization of MMA with the PEO chloro macroinitiator and CuCl proceeded at approximately half the rate of bromo analogs. A faster rate of polymerization and controlled molecular weights with lower polydispersities were observed in bulk polymerization compared with polar and nonpolar solvent systems. In the bulk polymerization, the number‐average molecular weight by gel permeation chromatography (M_n,GPC) values were very close to the theoretical line, whereas lower than the theoretical line were observed in solution polymerizations. The macroinitiator and their block copolymers were characterized by Fourier transform infrared spectroscopy, ¹H‐NMR, matrix‐assisted laser desorption ionization time‐of‐flight mass spectrometry, thermogravimetry (TG)/differential thermal analysis (DTA), differential scanning calorimetry (DSC), and scanning electron microscopy (SEM). TG/DTA studies of the homo and block copolymers showed two‐step and multistep decomposition patterns. The DSC thermograms exhibited two glass‐transition temperatures at ?17.7 and 92°C for the PEO and poly(methyl methacrylate) (PMMA) blocks, respectively, which indicated that microphase separation between the PEO and PMMA domains. SEM studies indicated a fine dispersion of PEO in the PMMA matrix. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 97: 989–1000, 2005     

Atom transfer radical polymerization synthesis and association properties of amphiphilic pullulan copolymers grafted with poly(methyl methacrylate)

Amphiphilic copolymers of pullulan grafted with poly(methyl methacrylate) (PMMA) were synthesized by atom transfer radical polymerization under homogeneous mild conditions without using protecting group chemistry. The hydroxyl groups of pullulan were reacted with 2‐bromoisobutyryl bromide to prepare pullulan macroinitiators with various degrees of substitution. Kinetic study showed that the polymerization was first order. The copolymers were characterized using ¹H NMR spectroscopy and gel permeation chromatography. The molecular weights of the grafted chains were controlled and polydispersities were low. Association properties in aqueous solution were studied using ¹H NMR spectroscopy, dynamic light scattering and transmission electron microscopy. Spherical nanoparticles with size and size distribution significantly affected by the number and length of the grafted chains were formed. Graft copolymers with a degree of substitution of 5.3% and length of PMMA grafted chains from 5 to 35 repeating units formed well‐defined quite monodisperse spherical nanoparticles with hydrodynamic diameters in the range 20–40 nm. This means that nanoparticle size can be tuned by changing the length of the grafted chains for this degree of substitution. Less control of aggregate size was obtained for a degree of substitution of 1.0%. Copyright © 2010 Society of Chemical Industry     

Preparation of monodisperse poly(methyl methacrylate) microspheres: effect of reaction parameters on particle formation, and optical performances of its diffusive agent application

A 3.84 um monodisperse poly(methyl methacrylate) (PMMA) microsphere was prepared by dispersion polymerization in methanol (MeOH)/water (H₂O) media. 2,2′-azobis(isobutyronitrile) (AIBN) and poly(acrylic acid) (PAA) were utilized as initiator and steric stabilizer, respectively. The effects of the PAA stabilizer, AIBN initiator, H₂O solvent and MMA monomer on PMMA particle size and size distribution were reviewed in the first section. The optical properties including total transmittance (T%) and transmittance haze (H%) were performed when the monodisperse PMMA microsphere was applied as a diffusive agent. The result was examined in terms of total interface area in system, and to compare with the performance of three polystyrene (PSt) microspheres with 1.10 um, 3.13 um and 5.21 um in diameter under the same condition.     

Grafting of poly(methyl methacrylate) or polyacrylonitrile onto polystyrene using ATRP technique

One of the most useful methods for synthesizing the graft and well‐defined copolymers is the atom transfer radical polymerization (ATRP) method. The polymerization was initiated by polystyrene (PS) carrying chloroacetyl groups as macroinitiator, in the presence of copper chloride (CuCl) and bipyridine (bpy). The macroinitiator (chloroacetylated PS) was prepared by successive chloroacetylation of PS under mild conditions and these reaction conditions overcome the problem of gelation and crosslinking in polymers. Successful graft copolymerizations were performed with methyl methacrylate (MMA) in toluene at 80°C and with acrylonitrile (AN) in tetrahydrofuran/ethylenecarbonate (62.5/37.5 v/v %) mixed solvent at 55°C. The characterization of the copolymers was investigated by ¹H‐NMR and FT‐IR spectroscopices. Gel permeation chromatography measurement indicated an increase of the molecular weight of the graft copolymers, as compared to that of the macroinitiator. This measurement also indicated the monomodal molecular weight distribution. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 100: 2619–2627, 2006     

Synthesis of poly(methyl methacrylate)-silica nanocomposites using methacrylate-functionalized silica nanoparticles and RAFT polymerization

Well-defined poly(methyl methacrylate)-silica nanocomposites were produced by “grafting through” using reversible addition-fragmentation chain transfer (RAFT) polymerization. The surface of silica nanoparticle was modified covalently by attaching methacryl group to the surface using 3-methacryloxypropyldimethylchlorosilane. Polymerization of methyl methacrylate (MMA) using the 4-cyano-4-(dodecylsulfanylthiocarbonyl)sulfanyl pentanoic acid RAFT agent, produced the PMMA-SiO₂ nanocomposites. Characterization of these well-defined nanocomposites included FT-IR, gel permeation chromatography (GPC), thermogravimetric analysis (TGA), differential scanning calorimeter (DSC), transmission electron microscopy (TEM) and dynamic mechanical analysis. These results show that the T_g values are higher and the mechanical strength of the PMMA-SiO₂ nanocomposites is slightly improved when compared to bulk PMMA. Further, the molecular weight of the PMMA (up to M_n = 100,000) is controlled and the SiO₂ are well dispersed in the PMMA matrix.     

Atom transfer radical polymerization of methyl methacrylate initiated with a macroinitiator of poly(vinyl acetate)

Well‐defined poly(vinyl acetate‐b‐methyl methacrylate) block copolymers were successfully synthesized by the atom transfer radical polymerization (ATRP) of methyl methacrylate (MMA) in p‐xylene with CuBr as a catalyst, 2,2′‐bipyridine as a ligand, and trichloromethyl‐end‐grouped poly(vinyl acetate) (PVAc–CCl₃) as a macroinitiator that was prepared via the telomerization of vinyl acetate with chloroform as a telogen. The block copolymers were characterized with gel permeation chromatography, Fourier transform infrared, and ¹H‐NMR. The effects of the solvent and temperature on ATRP of MMA were studied. The control over a large range of molecular weights was investigated with a high [MMA]/[PVAc–CCl₃] ratio for potential industry applications. In addition, the mechanism of the polymerization was discussed. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 1089–1094, 2006     

Solvent induced morphologies of poly(methyl methacrylate-b-ethylene oxide-b-methyl methacrylate) triblock copolymers synthesized by atom transfer radical polymerization

Poly(methyl methacrylate-b-ethylene oxide-b-methyl methacrylate) (PMMA-PEO-PMMA) triblock copolymers were synthesized using atom transfer radical polymerization (ATRP) and halogen exchange ATRP. PEO-based macroinitiators with molecular weight from M_n = 2000 to 35,800 g/mol were used to initiate the polymerization of MMA to obtain copolymers with molecular weight up to M_n = 82,000 g/mol and polydispersity index (PDI) less than 1.2. The macroinitiators and copolymers were characterized by gel permeation chromatography (GPC) and nuclear magnetic resonance (NMR) spectroscopy. The melting temperature and glass transition temperature of the copolymers were measured by differential scanning calorimetry (DSC). Crystallinities of the PEO blocks were determined from the WAXS patterns of both homopolymers and block copolymers, which revealed the fragmentation of PEO blocks due to the folding of the PMMA chains. Interestingly, the fragmentation was less pronounced when cast on surfaces compared to that in bulk, as measured by GISAXS. Solvent casting was used to control the morphology of the copolymers, permitting the formation of various states including amorphous, induced micellar with a PMMA core and flower-like PEO arms, and a cross-linked gel. Atomic force microscopy (AFM) was used to visualize the different copolymer morphologies, showing micellar and amorphous states.     

Effect of in situ polymerization conditions of methyl methacrylate on the structural and morphological properties of poly(methyl methacrylate)/poly(acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene)‐g‐styrene) PMMA/AES Blends

In this study, the structural and morphological properties of poly(methyl methacrylate)/poly(acrylonitrile‐g‐(ethylene‐co‐propylene‐co‐diene‐g‐styrene) (PMMA‐AES) blends were investigated with emphasis on the influence of the in situ polymerization conditions of methyl methacrylate. PMMA‐AES blends were obtained by in situ polymerization, varying the solvent (chloroform or toluene) and polymerization conditions: method A—no stirring and air atmosphere; method B—stirring and N₂ atmosphere. The blends were characterized by infrared spectroscopy (FTIR), transmission electron microscopy (TEM), and dynamic mechanical analysis (DMA). The results showed that the PMMA‐AES blends are immiscible and present complex morphologies. This morphology shows an elastomeric dispersed phase in a glassy matrix, with inclusion of the matrix in the elastomer domains, suggesting core shell or salami morphology. The occlusion of the glassy phase within the elastomeric domains can be due to the formation of graft copolymer and/or phase inversion during polymerization. However, this morphology is affected by the polymerization conditions (stirring and air or N₂ atmosphere) and by the solvent used. The selective extraction of the blends' components and infrared spectroscopy showed that crosslinked and/or grafting reactions occur on the elastomer chains during MMA polymerization. The glass transition of the elastomer phase is influenced by morphology, crosslinking, and grafting degree and, therefore, T_g depends on the polymerization conditions. On the other hand, the behavior of T_g of the glassy phase with blend composition suggests miscibility or partial miscibility for the SAN phase of AES and PMMA. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Phase behavior and properties of poly(methyl methacrylate)/poly(vinyl acetate) blends prepared via in situ polymerization

Polymer blends composed of poly(methyl methacrylate) (PMMA) and poly(vinyl acetate) (PVAc) were prepared via radical-initiated polymerization of methyl methacrylate (MMA) in the presence of PVAc. Differential scanning calorimetry and dynamic mechanical analysis were employed to investigate the miscibility and phase behavior of the blends. The PMMA/PVAc blends of in situ polymerization were found to be phase separated and exhibited a two-phase structure, although some chain transferring reaction between the components occurred. The phase separation resulted from the solvent effect of MMA during the in situ polymerization, which was confirmed by the investigation of phase behavior based on solution cast blending. Solubility analysis of the polymerized blends indicated that some chain transferring reaction between the components occurred during the polymerization. An abrupt increase in gel content from 21.2 to 72.4 wt % was observed when the inclusion of PVAc increased from 30 to 40 wt %, and the gel component consisted of the component polymers as shown by infrared spectroscopy studies. The thermogravimetric analysis study indicated that the inclusion of a small amount of PVAc gives rise to a marked stabilization effect on the thermal stability. The PMMA/PVAc blends exhibited increased notched impact properties with the inclusion of 5 wt % PVAc. © 1998 John Wiley & Sons, Inc. J Appl Polym Sci 69: 675–684, 1998     

Poly(methyl methacrylate) nanoparticles prepared through microwave emulsion polymerization

The emulsifier‐free emulsion polymerization of methyl methacrylate (MMA) was conducted with microwave irradiation. Superfine and monodisperse poly(methyl methacrylate) (PMMA) microspheres were obtained. Microwave irradiation notably promoted the polymerization reaction. This phenomenon was ascribed to the acceleration of the initiator [potassium persulfate (KPS)] decomposition by microwave irradiation. The experimental results revealed that the apparent activation energy of KPS decomposition decreased from 128.3 to 106.0 kJ/mol with microwave irradiation. The average particle size of the prepared PMMA latex was mainly controlled with the MMA concentration; it increased linearly from 103 to 215 nm when the MMA concentration increased from 0 to 0.3 mol/L and then remained almost constant at MMA concentrations of 0.3–1.0 mol/L. The KPS concentration had no effect on the average particle size, but the particle size dispersity was significantly reduced by a high KPS concentration. With a mixed polymerization phase (water/acetone = 1:3 v/v) or a redox initiation system, PMMA nanoparticles were obtained with an average particle size of 45 or 67 nm, respectively. © 2004 Wiley Periodicals, Inc. J Appl Polym Sci 93: 2815–2820, 2004     

Synthesis of nanosize poly(methyl methacrylate) microlatexes with high polymer content by a modified microemulsion polymerization

Summary Nanosize poly(methyl methacrylate) (PMMA) microlatexes with high PMMA/surfactant ratio have been successfully prepared by a modified microemulsion polymerization, i.e., continuous and slow addition of monomer (MMA) to the polymerizing MMA microemulsion with mild stirring. Number-average diameters of 33–46 nm with narrow polydispersity (D_v/D_n= 1.1) and polymer content of 6–24 wt% were achieved using low levels of surfactant (dodecyltrimethylammonium bromide, DTAB) — less than 1 wt% of the reaction mixture. Particle diameter depended on polymerization temperature, MMA content, and concentrations of initiator and surfactant. Larger particles wereformed when temperature was too high, initiator concentration was too high, or surfactant concentration was too low. Received: 24 February 1998/Accepted: 24 March 1998     

Investigation on the miscibility of the blends of poly(methyl methacrylate) and poly(styrene‐co‐acrylonitrile)

The miscibility was investigated in blends of poly(methyl methacrylate) (PMMA) and styrene‐acrylonitrile (SAN) copolymers with different acrylonitrile (AN) contents. The 50/50 wt % blends of PMMA with the SAN copolymers containing 5, 35, and 50 wt % of AN were immiscible, while the blend with copolymer containing 25 wt % of AN was miscible. The morphologies of PMMA/SAN blends were characterized by virtue of scanning electron microscopy and transmission electron microscopy. It was found that the miscibility of PMMA/SAN blends were in consistence with the morphologies observed. Moreover, the different morphologies in blends of PMMA and SAN were also observed. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2011     

About morphology in ethylene-propylene(-diene) copolymers-based latexes

Coatings and engineering plastics often require high impact strength. This property can be achieved with tougheners. For the present paper, core-shell impact modifiers were synthesized using ethylene-propylene copolymers (EPM), ethylene-propylene-diene copolymers (EPDM) or a mixture of both types (EP(D)M) as core material, as well as poly(methyl methacrylate) (PMMA) as shell material.EP(D)M-based polymers were dispersed in water using an Ultra-Turrax^® and a high pressure homogenizer. The prepared artificial latexes were used, either without further treatment or after crosslinking, as seed latexes in the emulsion polymerization of methyl methacrylate (MMA). The free radical seeded emulsion polymerization of MMA was investigated in the presence of an oil-soluble initiator, i.e. cumene hydroperoxide (CHP), combined with a redox system, i.e. sodium formaldehyde sulfoxylate hydrate (SFS), disodium salt of ethylenediamine tetra-acetic acid (EDTA), iron (II) sulfate heptahydrate (FeSO₄). This initiation system promotes polymerization of MMA near the surface of the seed particles, partially suppressing homogeneous secondary nucleation and polymerization in the aqueous phase.Kinetic and thermodynamic considerations were used to predict the particle morphology. The monomer type, the monomer-to-rubber ratio, the monomer feed type, and crosslinking of the seed latex particles were investigated, to optimize the polymerization kinetics and the properties of the resulting dispersions. The particle morphology was determined by cryo-transmission electron microscopy (cryo-TEM). Monomer-flooded conditions led to the formation of inverted core-shell particles, whereas starved-feed MMA or MMA/styrene mixtures gave rise to partially engulfed structures, i.e. snowman-like. Crosslinking of the EP(D)M seed particles was found to be required to provide the desired core-shell structures.Finally, the obtained core-shell structured particles were used to toughen a PMMA matrix. The tensile properties of the modified PMMA matrix were investigated. The micro-morphology of modified PMMA was studied by scanning electron microscopy (SEM). Tensile tests as well as TEM and SEM analyses demonstrated that the main mechanism of deformation operating in the EP(D)M-toughened PMMA matrix is shear yielding, accompanied by debonding and cavitation processes.     

Preparation of poly(methyl methacrylate)/titanium oxide composite particles via in‐situ emulsion polymerization

Poly(methyl methacrylate) (PMMA)/Titanium oxide (TiO₂) composite particles were prepared via in‐situ emulsion polymerization of MMA in the presence of TiO₂ particles. Before polymerization, the TiO₂ particles was modified by the silane coupling agent, which is crucial to ensure that PMMA reacts with TiO₂ via covalent bond bindings. The structure of the obtained PMMA/TiO₂ composite particles was characterized using Fourier transform infrared spectra (FTIR) and thermogravimetric analysis (TGA). The results indicate that there are covalent bond bindings between PMMA macromolecules and TiO₂ particles. Based on these facts, several factors affecting the resulting PMMA/TiO₂ composite system, such as the type of coupling agents, the mass ratio of the MMA to the modified TiO₂, the emulsifier concentration, and the initiator concentration, etc., were examined by the measurement of conversion of monomers, the gel content of polymers, the percentage of grafting, and the grafting efficiency, using gravity method or TGA method. As a result, the optimized recipe was achieved, and the percentage of grafting and the grafting efficiency could reach 216.86 and 96.64%, respectively. In addition, the obtained PMMA/TiO₂ composite particles were found to a stable colloidal dispersion in good solvent for PMMA. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 4056–4063, 2006     

Mechanistic study of the formation of amphiphilic core-shell particles by grafting methyl methacrylate from polyethylenimine through emulsion polymerization

The mechanism for the formation of amphiphilic core-shell particles in water is elucidated via a kinetic study of semi-batch polymerization of methyl methacrylate (MMA) grafted from polyethylenimine (PEI) initiated with tert-butyl hydroperoxide in an emulsion polymerization. The monomer conversion, the polymerization kinetics, the particle size, the particle number density, the poly(methyl methacrylate) (PMMA) core diameter, the percentage of unbound PEI, and the grafting efficiency of PMMA were determined at various times during the polymerization. The particle number density and the percentage of unbound PEI were almost independent of the controllable variables. The particle sizes and the core diameters increased with each consecutive batch of monomer addition, while the grafting efficiency of PMMA decreased. These data supported the hypothesis that the PEI-g-PMMA graft copolymers were formed early in the polymerization and later self-assembled to a new phase, micellar microdomains. These microdomains act as loci for subsequent MMA polymerization as the monomer is fed into the reaction, without subsequent formation of new particles. The size of the resulting highly uniform core-shell particles (99-147 nm) can be controlled by choosing the amount of monomer charged. Thus, this polymerization method is viable for a large scale production of core-shell particles with high solids content.     

Dispersion polymerization of MMA in supercritical CO2 in the presence of poly(poly(ethylene glycol) methacrylate-co-1H,1H,2H,2H-perfluorooctylmethacrylate)

Various random copolymers of poly(poly(ethylene glycol) methacrylate-co-1H,1H,2H,2H-perfluorooctylmethacrylate) (p(PEGMA-co-FOMA)) with different poly(ethylene glycol) (PEG) chain length (M_n = 300, 475, and 1100) and different FOMA content have been synthesized in supercritical carbon dioxide (scCO₂) via free-radical polymerization. The copolymers containing above 50 wt% FOMA could be used as a stabilizer for the polymerization of methyl methacrylate (MMA) in scCO₂. For PEGMA (300) and PEGMA (475) copolymers, the copolymeric stabilizer with 67–69 wt% FOMA content was shown to be optimal to produce micrometer-size spherical PMMA powder. The size of pendant PEG group and the composition of copolymer as well as the concentration of MMA affected on the size of PMMA particles and the stability of PMMA latexes in CO₂.     

Poly(ethylene glycol) as a ‘green solvent’ for the RAFT polymerization of methyl methacrylate

We demonstrate the use of a range of poly(ethylene glycol)s (PEGs) to control the polymerization of methyl methacrylate (MMA) using reversible addition-fragmentation chain transfer (RAFT) polymerization. The use of PEG as the solvent (M_n = 4600 g mol⁻¹) resulted in an increase in the rate of the reaction over that of other solvents by a factor of 5 at 60 °C, allowing MMA to be polymerized to high conversions with a DP of 100 much more rapidly than in standard solvents, while maintaining control over the molecular weight with polydispersities as low as 1.05. Interestingly, whilst the same rate increase is seen when polymerizing to a DP of 500, PEG appears to limit the achievable molecular weight to differing degrees depending on its chain length. Advantages of using PEG include its very low toxicity and other environmentally friendly aspects of its nature that allow it to be classed as a ‘green’ solvent.